1. Technical Field
This invention relates to a pipeline inspection apparatus, and in particular to an apparatus for inspecting a lateral branch of a pipeline.
2. Discussion of the Prior Art
Pipeline installations such as those for sewage generally comprise a main pipeline having lateral branches extending therefrom, for connecting individual buildings to the pipeline. Lateral branches may require inspection if, for instance, it is suspected they are damaged. If a lateral branch is damaged, there may be undesirable consequences such as contamination of ground water by leaking sewage, or infiltration of ground water into the sewage pipeline which subsequently increases the burden on sewage treatment plants. However, locating the damage is a difficult task because lateral branches are usually not straight and may be considerably long (e.g. 100 meters).
To inspect such lateral branches, a miniature inspection device such as a video camera may be attached to an end of a semi-rigid member, and the camera may be introduced and pushed into the lateral branch from an access point inside the building. This method of inspection is inconvenient because arrangements must be made with the occupants to enter the building. Moreover, the process of inspecting a number of lateral branches corresponding to a single main pipeline is inefficient because each branch must be inspected separately from within each successive building.
To overcome the above difficulties, apparatus have been proposed for remotely inspecting lateral branches from within a main pipeline. For example, U.S. Pat. No. 4,651,558 to Martin and Guthrie relates to a launcher which is pulled through a main pipeline using ropes or cables. The launcher has an aperture from which a miniature video camera may be advanced into a lateral branch. The launcher is substantially cylindrical and is rotatable about its longitudinal axis so as to align the aperture with a lateral branch of the pipeline. Once such alignment is achieved, the video camera, which is fixed to an end of a semi-rigid push rod, is advanced into the lateral branch by means of motor-driven pinch rollers contained in the launcher. The rollers grip the rod and propel it forward as they are rotated.
U.S. Pat. No. 4,677,472 to Wood describes another apparatus for advancing a miniature video camera, fixed to an end of a semi-rigid push rod, into a lateral branch of a pipeline. The apparatus, which is pulled through a main pipeline, employs a pair of motor-driven drive pulleys through which the push rod is advanced into the lateral branch. The pulleys are tiltable and rotatable so that the position from which the video camera is advanced may be aligned with a lateral branch.
There a several drawbacks of the above-described prior art apparatus. For instance, both employ motors and complex mechanical arrangements of pulleys or rollers for advancing the push rod and camera into the lateral pipe. As a result, they are limited in power and hence in the length of a lateral branch through which an inspection camera may be advanced. Further, they are bulky, and expensive to manufacture and maintain.